Rotary tension device for sewing machines



p 19, 1961 c. R. BACKLIN 3,000,591

ROTARY TENSION DEVICE FOR SEWING MACHINES Filed Oct. 7, 1958 2Sheets-Sheet 1 Z4 Z5 35 '27 INVENTOR.

Sept. 19, 1961 c. R. BACKLIN ROTARY United States Patent v 3 cc FiledOct. 7, 1958, Ser. No. 765,794 2 Claims. (Cl. 242-155) The presentinvention relates to rotary take-up devices for sewing machines.

With the advent of high speed sewing machines and the use of syntheticthreads, problems of tensioning said threads during a sewing operationhave arisen. With synthetic threads, they are more elastic or stretchierthan the conventional cotton threads and hence the tensions must be moresensitive so that they Will not distort the threads. With threads, suchas cotton or silk which are not properly surface finished, tensiondevices, particularly in high speed sewing machines, must be employedwhich minimize friction upon the thread.

It is an object of the present invention to provide a sensitive rotarytension device which is capable of producing very light tensions on athread and also one which provides more positive traction without unduesurface friction on the thread such as might cause inadvertent breakagethereof.

This is accomplished, according to the present invention, by providing atension device with lightweight parts and a unique tension wheel andbrake means therefor. While aluminum and other similar materials may beused for the tension wheel and coacting parts, it is at presentpreferred to use nylon because of its lightness in weight and its freerunning without the need of lubricants. The unique tension wheel has aperipheral thread-receiving groove and the groove is provided withrecesses in the bottom thereof to produce a more positive traction ofthe thread therewith to rotate the same. Preferably, the recesses areformed by holes passing through the tension wheel and intersecting thebottom of the groove as this structure also lightens the weight of thetension wheel.

Other features and advantages of the invention will be apparent from thespecification and claims when considered in connection with theaccompanying drawings in which:

FIGURE 1 shows a back view of the head portion of a sewing machineshowing the tension device in position thereon.

FIG. 2 shows an end view of the sewing machine head of FIG. 1.

FIG. 3 shows a longitudinal sectional view through the tension deviceand mounting boss.

FIG. 4 shows an enlarged sectional view of the tension wheel.

FIG. 5 shows a side view of the tension housing.

FIG. 6 shows a side view of the tension stud.

FIG. 7 shows a side view of the outer disk.

As shown in FIG. 1, the rotary device 10 of the present invention ismounted on a head 11 of a sewing machine 12 and is disposed in amounting boss 13 provided thereon so that it projects rearwardly beyondthe head and in position to engage a thread 14 fed thereto from a supply(not shown) through a preliminary light tension means 15 and guide 16.The thread, after leaving the tension device, passes under a fixed guide17, to the rotary take up 18 of the machine, and from the-rotary takeupto the sewing needle 19. The head carries the usual tension release pin20 which cooperates with the tension device to release the tension onthe thread when the usual presser foot lever 21 is raised to move thepresser foot (not shown) out of contact with the material being sewn.

The tension device as shown in the drawings com- Patented Sept. ,19,1961 prises a tension housing 22, as shown in FIGS. 3 and 5, adapted tobe mounted in a bore 23 in the boss 13 and secured therein by a setscrew 24. It has an enlarged head 25 at the forward end and is providedwith a bore 26 in which a tubular tension stud 27, shown in FIG. 6, ismounted. The stud is fixed to the housing by a set screw 28. The tensionstud has an enlarged section 29 which is adapted to be positioned inspaced relation with the walls of an enlarged portion 30 of bore 26 inthe housing and is provided on its outer end with a portion 31 ofreduced diameter having a bifurcated end 32 which is threaded at 33.Mounted for rotation on the tension stud is a tension wheel 34 and apair of tension or braking washers 35, 36. The inner tension washer 35engages the face of the enlarged section 25 of the housing and one faceof the tension wheel. The other tension washer 36 engages the other faceof the tension Wheel and is engaged by an outer tension disk 37 which isslidably mounted on the end of the stud and is provided with across-piece 38 which extends through the kerf forming the bifurcated endof the stud to prevent rotation of the disk on the stud. A light tensionspring 39 surrounds the hub 40 of the outer disk and has its other endengaged by a knurled nut 41 threaded on the end of the bifurcated stud.

With this arrangement it will be seen that the spring causes the outerdisk to press the tension washer 36 against the tension wheel 34 and thesecond tension washer 35 against the enlarged section 25 of the fixedhous ing, thus applying a braking action to the tension wheel to retardits rotation by the thread passing thereover and to produce the requiredtension on the thread.

By adjusting the pressure of the spring by the knurled nut 41 it will beseen that the amount of tension pressing the outer disk to clamp thetension Wheel and braking washers between it and the housing will bevaried and alter the braking action on the rotating tension wheel. Theresistance to rotation by the thread as it is fed tothe needle duringthe sewing operation provides the required tension in the thread duringthe sewing operation. I

While the lightweight tension wheel and associated elements, such as thetension washers and outer disk, may be made of aluminum, fiber or thelike, it is at present preferred to form them of nylon which may be.readily formed, is light in weight, and has smooth contacting surfaceswhich are free running without requiring lubricants. This results in ahighly sensitive lightweight device for accurately controlling thetension on the thread. I

A feature of the present invention resides in the construction of thetension wheel which includes a peripheral thread-engaging groove 42,preferably a V-shaped groove, and has a plurality of recesses 43 formedin the bottom wall of the groove. Thus when the thread is wound once ortwice around the wheel it will have greater traction with the wheel.This will be clear from FIG. 4 of the drawings in which it will beapparent that the thread is supported by the arcuate surfaces 44 betweenthe recesses and extends in a straight line between the edges of saidsurfaces as it passes over the recesses. In this way the thread is givenan added traction with the wheel since the edges of the recesses providefeeding surfaces for engagement by the thread to enhance the tractionwith the wheel. However, the edges are not sufficiently sharp to have anabrasive action on the thread as it passes therethrough.

While the recesses may be formed in many ways, it is at presentpreferred to form them as transversely extending holes 45 passingthrough the tension wheel. As herein illustrated the holes are arrangedin an annular row with the walls of the holes intersecting the bottom ofthe groove to provide the recesses between the arcuate surfaces. Thisgreatly simplifies the manufacture of the 3 wheel, particularly whennylon or the like lightweight plastic material is employed.

If desired, a check spring 46 can be provided on the device and asherein illustrated in FIG. 4, it is mounted in the enlarged bore 30 ofthe tension housing surrounding the stud portion 29; It has one endanchored to the stud and the other end is formed into a check loop 47extending outwardly therefrom through slot 25a in the housing to overliethe tension wheel and yieldingly support the thread as it passes fromthe tension device to the fixed guide 17. This tends to keep the threadtaut as it passes from the tension wheel to the rotary take-up 18 duringthe starting and stopping of the sewing machine and eliminates any sharppulls or jerks in the thread which might cause the thread to break.

If desired, the tension housing and outer disk can be provided withbevelled edges as shown at 48, 49 in FIG. 3 which overlie the sides ofthe tension wheel and serve to guide the thread into the peripheralgroove as the thread is wound into place on the tension device during athreading-up of the machine.

When it is desired to release the braking action of the device on thepassage of thread therethrough, the tension release pin 20 is operatedto the conical head thereof to engage a stud release pin 50 carried inthe tubular stud so as to project at one end beyond the end of thetension stud. The other end of the stud release pin bears against thetransverse portion 38 of the outer disk and is operated to move the diskoutwardly and release the pressure of the tension spring from thetension washers and tension wheel whereby the tension wheel is free torotate as the thread is pulled therethrough.

It will be seen, therefore, that I have provided a novel tension devicewhich is lightweight in construction and smooth and sensitive in itsoperation whereby an accurate control of the tension may be had on asewing thread during the sewing operation to prevent stretching ofsynthetic fibers or undue breaking of cotton or silk fibers which donothave surface lubrication thereon.

A feature of the present invention resides in the novel friction wheelwhich is preferably of unitary construction and having an improvedtraction surface for the thread which is wrapped therearound and tendsto rotate the wheel against the braking action of the tension device toproduce the accurate control of the tension on the thread.

Variations and modifications may be made within the scope of the claimsand portions of the improvements may be used without others.

I claim:

1. In a rotary tension device for a high speed sewing machine, a tensionhousing adapted to be mounted on a sewing machine and having a tubulartension stud fixed 4 therein to project therefrom, said stud having ashoulder thereon and a bifurcated end portion, a tension wheel having apair of braking washers on opposite sides thereof rotatably mounted onthe stud with one washer engaging the housing, an outer disk slidable onthe stud and having a portion cooperating with the bifurcated portion ofthe stud to prevent rotation thereof on the stud, and adjustable springmeans urging the outer disk toward the housing and applying brakingpressure on the tension wheel disposed therebetween, the improvementwherein said Wheel and braking washers are formed of nylon and saidwheel has a peripheral groove and has transverse spaced holes extendingthrough the wheel and intersecting the bottom of said peripheral groovewhereby a lightweight wheel having improved thread traction is provided.2. In a rotary tension device fora high speed sewing machine, a tensionhousing adapted to be mounted on a sewing machine and having a tubulartension stud fixed therein to project therefrom, said stud having ashoulder thereon and a bifurcated end portion, a tension wheel having apair of braking washers on opposite sides thereof rotatably mounted onthe stud with one washer engaging the housing, an outer disk slidable onthe stud and having a portion cooperating with the bifurcated portion ofthe stud toprevent rotation thereof on the stud, and adjustable springmeans urging the outer disk toward the housing and applying brakingpressure on the tension wheel disposed therebetween, the improvementwherein said outer disk, wheel and braking washers are formed of nylonand said wheel has a V-shaped peripheral groove and has an annular rowof transverse holes extending through the wheel and intersecting thebottom of said peripheral groove whereby a lightweight wheel havingimproved thread traction is provided.

References Cited in the file of this patent UNITED STATES PATENTS614,973 Ostrom Nov. 29, 1898 1,029,923 Freese June 18, 1912 2,624,527Von Kohorn Jan. 6, 1953 2,720,365 Kolvalchik et a1. Oct. 11, 19552,764,367 Brey' Sept. 25, 1956 2,810,532 Zeier et al Oct. 22, 1957 OTHERREFERENCES Product Engineering, Nylon in Bearings and Gears, July 1950,pages 102-107.

Plastics Bulletin, Nylon Plastic For Mechanical Parts, volume 12, 1950,pages 187-190.

Materials and Methods, Pressed and Sintered Nylon Powder Parts, October1952, pages 108-111.

